Ceramic ball bearings and assembly

ABSTRACT

A ceramic ball bearing assembly ( 20 ) has raceway components generally held in residual compression by accompanying metal attachments. In a ceramic ball bearing assembly ( 20 ), an outer raceway ( 22 ) is formed that is held in compression by a circumscribing steel ring. The components may be fitted together with the ceramic raceway subject to thermal contraction while the steel ring is subject to thermal expansion. Upon mating, the ceramic raceway ( 22 ) slightly expands while the steel ring slightly contracts to impose residual compression upon the ceramic raceway. The residual compression preserves the ceramic raceway despite thermal or other stresses of operating environment. An inner ceramic raceway ( 24 ) is constructed by employing one of several of the herein described methods, and the ceramic ball bearing assembly of the present invention may use balls ( 26 ), needles, cylinders, or other rolling elements to in order to achieve smooth angular translation between the inner and outer ceramic raceways.

TECHNICAL FIELD

[0001] This invention relates to ball bearings and the like for use inmechanical structures including aircraft, and more particularly to aceramic ball bearing assembly that provides ceramic-on-ceramicoperation.

BACKGROUND ART

[0002] Current manufacturing practices used in the manufacture of ballbearings result in difficulties associated with allowing 100% of thecontact surfaces to be ceramic material. This limitation is driven bythe difficulty to mount low tensile strength, high Young's modulus, lowthermal expansion rate ceramic rings on to steel shafting as thecorresponding characteristics of the steel shafting are incompatiblewith those of ceramic rings. Ceramic rings are sensitive to tensilestresses which can result in destructive overload failure. For high DNapplications and for application across large temperature regimes, thecurrent state of the art is to use ceramic balls with steel racewayrings. Ceramic balls have lower adhesive tendencies than all-steel ballsand high hot hardness. The achievement of a robust all-ceramic bearingwould result in an operating advantage over partially, or hybrid,ceramic bearings in high-speed, high temperature low lubrication, and/orhot environments.

[0003] Consequently, it would be of some advantage to provide a robustmeans by which 100% of the contact surfaces in a ball bearing or thelike could be ceramic. As indicated above, mounting ceramic ringsdirectly on steel shafting tend to destroy the ceramic rings due tooperating incompatibilities. Consequently, it would be an advance in theart to provide ceramic ball bearings and assemblies thereof that werecompatible with steel drive shafts, other steel shafts, and the like.

DISCLOSURE OF INVENTION

[0004] The present invention provides low-cost ceramic ring/steel ringassemblies that can be achieved through the application of brazetechnology, creating residual compressive loading of the ceramic ringwith the high load capacity steel. A steel ring circumscribing the outerdiameter of a ceramic outer raceway will shrink more while cooling downfrom braze temperature than the ceramic ring in the assembly. Thisresults in residual compression in the steel-rim hoop structure in bothhoop and axial directions in the ceramic ring. Ceramics are generallymaterials that withstand compression well but may suffer destructivelyif subject to tension or tensile forces. Consequently, by using thesteel ring's material characteristics to create residual compressionupon the ceramic ring, the ceramic ring can be protected fromdestructive tensile forces.

[0005] For an inner ceramic ring or raceway, a steel ring on the insideof a ceramic inner raceway shrinks more during cool down from brazetemperature than the circumscribing ceramic ring. Therefore suitablemeans are required for managing, the residual compression in both hoopand axial directions in the ceramic ring.

[0006] Residual compressive stress, when properly managed, can serve toprotect the weak-in-tension but strong-in-compression ceramic rings fromcracking during operation, as well as during a press-fit mounting of theceramic bearing assembly. A bearing which properly manages the ceramicresidual stresses enables a ceramic ball bearing with 100% of thecontact surfaces being ceramic materials to be achieved as opposed tothe current state-of-the-art hybrid system with a ceramic ball and steelraces. Braze technology set forth herein also enables the use ofsegmented ceramic ring segments if required due to dissimilar thermalexpansion, centrifugal loading, or other operating characteristics.

[0007] In an alternative embodiment of the present invention, an inversehybrid configuration may be achieved where a steel ball bearing runsagainst the ceramic raceway. The technical advantage to this embodimentis that a difficult-to-machine steel material can be used for therolling ball using existing mass production techniques which reduce thecost for such steel balls. In conjunction with ceramic raceways, theceramic tribological (low-wear, low-lubrication requirements) contactadvantages are maintained by the ceramic rings. The contact stresses arereduced by the use of steel balls having a low Young's modulus. Suchsteel balls may be made of GB42, Cobalt alloys, or be hollow.

[0008] In a third alternative embodiment, AES (Aircraft Engine System)high temperature unlubricated valve bearings may be achieved. Low-cost,high-temperature ceramic ring/steel ring assemblies can be achievedthrough the application of high-temperature braze technology to createresidual compressive loading of the ceramic ring coupled with a highload capacity steel outer or inner ring. This enables a true ceramicball bearing as opposed to current state-of-the-art ceramic hybridbearings with ceramic balls turning in steel races. Such ceramic ballbearings set forth herein offer increased wear and erosion resistance,which is a significant problem in the field. Such ceramic ball bearingshave the potential to be significantly advantageous for AES hightemperature valves.

[0009] Other features and advantages of the present invention willbecome apparent from the following description of the preferredembodiment(s), taken in conjunction with the accompanying drawings,which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF DRAWINGS

[0010]FIG. 1 is a side cross-sectional view of a ceramic ball bearingassembly of the present invention.

[0011]FIG. 2 is a side cross-sectional and partially perspective view ofan embodiment of the present invention using a castellated steel sleeve.

[0012]FIG. 3 shows a side cross-sectional and partially perspective viewof the ceramic ball bearing assembly shown in FIG. 2 with thecastellated projections wrapped to engage the ceramic ring.

[0013]FIG. 4 is a side cross-sectional view of an alternative embodimentof the present invention showing an inner ceramic raceway coupled to asteel ring via expandable and contractable bellows.

[0014]FIG. 5 is a partial cross-sectional view of an inner ceramicraceway coupled to a steel ring by rod-like structures and a spring.

[0015]FIG. 6 shows a schematic view of a coaxial and concentric steelring and ceramic raceway pair disposed with respect to one another viairis-like articulation.

[0016]FIG. 7 is a partial cross-sectional view of an inner ceramicraceway coupled to an inner steel ring having inwardly-folded sideprojections.

[0017]FIG. 8 is cross-sectional view of an inner ceramic racewayconstructed in a manner similar to that shown in FIG. 7.

MODE(S) FOR CARRYING OUT THE INVENTION

[0018] The detailed description set forth below in connection with theappended drawings is intended as a description of presently-preferredembodiments of the invention and is not intended to represent the onlyforms in which the present invention may be constructed and/or utilized.The description sets forth the functions and the sequence of steps forconstructing and operating the invention in connection with theillustrated embodiments. However, it is to be understood that the sameor equivalent functions and sequences may be accomplished by differentembodiments that are also intended to be encompassed within the spiritand scope of the invention.

[0019] The present invention achieves bearings having 100% of thecontact surfaces being ceramic material. Such bearings have significantadvantages over regular steel or “hybrid” ceramic-and-steel bearings forhigh-speed, high temperature, low lubrication and/or hot environments.

[0020] One of the significant problems with respect to creating a robustceramic bearing capable of operating over wide temperature and DNregimes is to manage tensile forces developed during the operating ofthe ceramic bearing so that the forces do not destroy the bearing. Asset forth in more detail below with respect to construction andoperation of the ceramic ball bearings and assembly of the presentinvention, the problem of tension upon the ceramic raceways has beenresolved by delivering a protective carriage or chassis in the form of asteel raceway in a variety of different geometries. Even thoughoperating conditions may cause thermal or other expansion of theassembly, the configurations set forth allow for management of thetensile pressures or forces which result from such expansions, thuspreserving the integrity of the ceramic raceway and creating greaterreliability and less risk of destruction of the ceramic raceway. Tensilepressures may also occur due to expansion of adjoining parts, such as asteel shaft press fitted through the steel mounting rings. The presentinvention also takes such adjoining part expansion into account in orderto preserve and maintain the ceramic raceways (the residual compressivestress in the ceramic prevents the ceramic ring from being placed intension).

[0021] Turning now to FIG. 1, one embodiment of the present invention isshown. The ceramic ball bearing assembly 20 of FIG. 1 has an outerraceway 22, an inner raceway 24, one or more ceramic ball bearings orother rolling elements 26, and oppositely-opposed, laterally-adjacentsteel rings 28, 30.

[0022] Absent from FIG. 1 is an outer steel ring or the like. Generally,the construction of an outer ceramic raceway for a ceramic ball bearingis achieved by shrink fit techniques such that positive interference ismaintained throughout the entirety to predicted operating range, andsuch that the stresses generated from such an interference fit do notcause catastrophic residual stresses in the ceramic or yielding in themetal.

[0023] Alternately, another suitable mechanical of chemical bondingtechnique can be used to attach an outer steel ring to the outer ceramicring 22.

[0024] With respect to the construction of the inner raceway as shown inFIG. 1, the fabrication process is as follows: A ceramic inner raceway24 is bonded to a complement of laterally facing washers 30, 28 by meansof a suitable brazement 34. The brazement consist of an series of layerswhich allow for chemical bonding and for residual stress management.Such brazement may be according to U.S. patent application Ser. No.09/782,865 filed Feb. 13, 2001 and/or U.S. Pat. No. 6,131,797 issuedOct. 17, 2000 to Gasdaska et al. entitled “Method for joining ceramic tometal which are incorporated herein by this reference thereto. The '865patent application discloses brazing with molybdenum rings as well asmolybdenum and nickel rings. The '667 patent discloses brazing usingmolybdenum for joining ceramic to metal.

[0025] To accomplish the chemical bond, and the stress management, Theattachment between the steel rings 28, 30 and the inner ceramic racewayring 24 incorporates a braze joint-interlayer system,. Such aninterlayer system may include the use of alternative layers ofbraze-molybdenum-braze as well as braze-nickel-braze-molybdenum brazeand has been shown capable of accommodating the stresses with acceptablereliability. In some embodiments, the interlayer system may or may notuse a nickel layer. Care must be taken during the construction processto maintain detail alignment. In fabricating the ceramic ball bearingassembly 20 of FIG. 1, the tolerances need not be precise to a highdegree as post-braze machining can be used to achieve the finaldimensions. During service, when the bearing assembly 20 is put to use,the thermal expansion of a shaft passing through the center aperture 32of the bearing assembly 20 causes a change in the stress state in theinner race assembly, however, due to design of the ceramic-metalinterface 34, and the overall component design, the stress state in boththe metal and the ceramic remains acceptable.

[0026] Note should be taken that the steel rings 28, 30 have a smallerinner diameter than the inner ceramic raceway ring 24. This causes thesteel rings 28,30 to enjoy a certain thrust or extension 34 past theinner surface 36 of the inner ceramic raceway 24. This enables the steelrings 28, 30 to engage a drive shaft or the like passing through thecenter aperture 32 of the bearing assembly 20. When the shaft (notshown) expands, it is the steel rings 28, 30 that bear the brunt of suchexpansion. In FIGS. 2 and 3, an alternative embodiment of the presentinvention is shown using a castellated steel tube having projectingparapets that are used to engage an inner ceramic raceway surrounded bywedges which allow some spatial accommodation for the entrapped innerceramic raceway ring.

[0027] As shown in FIG. 2, the inner raceway assembly 50 has an innersteel tube 52 which is castellated in that it has oppositely opposedparapets 54, 56, each parapet having alternating merlons 58 and crenels60.

[0028] The center area 62 of the inner steel tube 52 is generally solidin nature in order to support the inner ceramic raceway 64. As shown inFIG. 2, the inner ceramic raceway 64 has the form of a biased hexagon incross section with the outer portion of the hexagon predominating overthe inner portion. A lower pair of wedge rings 70, 72 engage the innerceramic ring 64 on opposite sides of the ceramic ring 64. A pair ofupper wedge rings 74, 76 engage opposed outer hexagon sides of the innerceramic ring 64. The lower hexagon surface 78 engages the center portion62 of the inner steel tube 52, while the upper hexagon surface 80 servesas a platform or raceway for the rolling elements such as balls,needles, cylinders or other rollers, or the like.

[0029] The upper and lower wedges 70, 72, 74, 76 may be ring orring-like in nature or they may be constructed in alternativeembodiments to correspond to the merlons 58 of the parapets 54, 56.

[0030] As shown in FIG. 3, the wedges 70,72,74,76 may be engaged bycorresponding merlons 58 that are folded or bent to engage the wedges70, 72,74,76. This allows the ceramic ring 64 to be entrapped by thewedges 70, 72, 74,76 which are themselves held in place by the in-foldedor in-bent merlons 58.

[0031] As shown in FIGS. 2 and 3, the wedges generally take a shape thataccommodates both the ceramic ring 64 and the corresponding merlons 58.With respect to the lower wedges 70, 72, the shape of the lower wedgesmay be determined by the surfaces engaging it so that it provides somelower engagement and maneuverability for the ceramic rings 64. The lower70,72 and upper 74, 76 wedges may engage one another and may alsoaccommodate one another in their surface engagements.

[0032] The upper wedge rings 74, 76 may have projections or extensionsinto which and around which the merlons 58 may fold. This providesbetter engagement by the merlons 58 of the upper wedge rings 74, 76, aswell as creating a spring effect for some resiliency for the merlons 58themselves, as well as in conjunction with the upper and lower wedgerings 74, 76.

[0033] For the embodiments shown in FIGS. 2 and 3, the inner steel tube52 is inserted into the ceramic rings 64. The parapets 54, 56,particularly the merlons 58 would be cold worked to capture the ceramicrings 64 via the wedges 70, 72, 74, 76. The wedges are used to allow theceramic rings 64 to “ride-up” when the assembly 50 is cold. When theassembly 50 cools down, each of the components shrinks. Yet due to thedifferent materials used in construction of each of the elements in theinner raceway assembly 50, they will each contract to a differentextent. As the assembly 50 thermally expands, the parts expand and thegap between the inner steel tube 52 and the ceramic ring 64 diminishes.

[0034] The inner steel tube 52 does not require precision machining, butsuch precision machine may be needed for the inner ceramic raceway ring64 and the wedges 70, 72, 74, 76. The merlons 58 are brazed to the upperwedges 74, 76. The ceramic rings 64 may also be brazed to the upperwedges 74, 76. However, no brazing may be needed for the lower wedges70, 72, either to the merlons 58 or the inner ceramic raceway ring 64.By careful design, the embodiments shown in FIGS. 2 and 3 might provideretrofitting of this embodiment to existing circumstances and workingenvironments.

[0035] The inner ceramic raceway assembly 90 shown in FIG. 4 has agenerally circular ceramic raceway ring 94 brazed by braze joints 96 toa flexible bellows-like structure 98. The opposite end of thebellows-like structure 98 is likewise brazed or joined by a brazed joint100 to an inner steel ring 102.

[0036] Tie-tabs, washers, or the like, may substitute for thebellows-like structure 98. The bellows-like structure 98 serves toprovide generally uniform separation of the ceramic raceway ring 94 fromthe inner steel ring 102.

[0037] The concentricity of the two rings 94, 102 may be provided bysprings, elastomeric filling, a rotating expansion cam mechanism (suchas that shown in FIGS. 5 & 6), or the like. Movement along the commonshared axis of the two concentric tubes 94, 102 may be provided by thestiffness of the bellows-like structure, tie-tabs, etc. 98. Thebellows-like or other attachment 98 between the inner ceramic racewayring 94 and the inner steel tube 102 is free to expand and contract bymeans of integral springs (such as those lending the bellows-likeshape), pin-in-tube arrangements, rod-in-loop arrangements (FIG. 5), orthe like. The bellows-like structure 98 may be made of sufficientlystiff yet sufficiently resilient material able to undergo the stressesof the environment in which the inner ceramic raceway 90 of FIG. 4operates.

[0038] In this configuration, no precision machining of parts may berequired. The sides of the ceramic raceway ring 94 may be metalized bybrazing to allow spot-welding, brazing, soldering, tapping, and the liketo enable attachment of an axial-motion restraint such as thebellows-like structure 98 shown in FIG. 4. If brazing or soldering isused to attach an axial-restraint system such as the bellows-likestructure 98 shown in FIG. 4, an alloy with a lower melting temperaturethan that used to metalize the ceramic should be used for the brazing orsoldering material. This prevents the melting of the metalization layerand promotes the attachment of the axial restraint system 98 to theinner ceramic raceway 94.

[0039] As shown in FIG. 6, if a rotating expansion cam system is used,pegs, rods, bars, or the like 110 may be attached to the inner surfaceof the ceramic raceway ring 94. Projecting arms of metal or othersubstances 112 may be used to entrap the pegs 110 between them. Theprojecting arms allow the inner steel ring 102 to turn with respect tothe inner ceramic raceway ring 94. The projecting arms 112 also serve tokeep the two rings 92, 102 coaxial and aligned. As the inner steel ring102 will expand more when heated, the swelling of the inner steel ring102 serves to push the projecting arms outward. As the travel of thearms is restricted by the pegs 110, the inner steel ring is kept incoaxial alignment with the ceramic raceway ring 94.

[0040]FIG. 5 shows an alternative embodiment of the inner racewayassembly. The inner raceway assembly 120 of FIG. 5 maintains the use ofthe steel tube or ring 122 with respect to the inner ceramic racewayring 124. The side of the inner steel ring 122 opposite that of theinner ceramic raceway 124 would be that placed against a drive shaft orthe like. Braze joints 126 are used to secure the inner ceramic raceway124 to loops 128. Traveling through these loops are rods 130, which arebrazed to the inner steel ring 122 by brazed joints 132.

[0041] While radial displacement of the inner ceramic raceway ring 124is limited with respect to the inner seal ring 122 due to the entirebearing assembly, the rods 130 and loops 128 serve to ensure there is noaxial movement, or movement along the shared central axis, between theinner steel ring 122 and the inner ceramic raceway 124. This limits themovement of the inner ceramic raceway ring 124 to motion parallel thatto the rods 130. In order to keep the inner ceramic raceway ring 124disposed away from the inner steel ring 122, springs or the like 134 maybe used to urge the inner ceramic raceway ring 124 away from the innersteel ring 122.

[0042] As shown in FIGS. 7 and 8, an alternative embodiment of the innerceramic raceway may be achieved by using an alternative inner ceramicraceway assembly 150. In this alternative embodiment of the innerceramic raceway assembly 150, an inner ceramic raceway ring 152 definesa gutter or depression 154. Rolling elements, including balls, needles,cylinders, and the like, may travel through the gutter 154 when engagedby the outer ceramic raceway ring (not shown). Arms 156, 158 may projectupwardly from underlying portions 160, 162 as part of an inner steelring assembly 164. The inner steel ring assembly 164 has a left partportion 166 (as viewed in FIG. 7) and a right part portion 168. The leftand right part portions 166, 168 thread or screw together by means ofthreaded engagement 174 in order to engage the inner ceramic raceway152. The arms 156,158 may be brazed or otherwise attached to the innerceramic raceway 152. A gap may or may not be present between the lowerportions 160, 162 of the inner steel ring assembly 164 and the bottom ofthe inner ceramic raceway ring 152.

[0043] In order to achieve the convolutions 172 of the left and rightarms 156, 158, scores such as that shown at 170 are used in order tomake the metal more easily bent or castellations as shown on 58 of FIG.3.

[0044]FIG. 8 shows a side cross-sectional view of an alternativeembodiment of the assembly shown in FIG. 7. Instead of convoluted arms,the inner raceway assembly 180 shown in FIG. 8 has a generallytrapezoidal ceramic inner raceway 182 entrapped by the inner steel ringassembly 184. The inner steel ring assembly 184 has left and right steelring portions 186, 188.

[0045] As shown in FIG. 8, the left and right steel ring portions extendinwardly to engage the sides of the trapezoidal inner ceramic raceway182. As the inner ceramic raceway 182 flares outwardly towards thecenter axis of the assembly 180, the complementary narrowing provided bythe left and right steel ring portions 186, 188 serve to entrap theinner ceramic raceway 182 within the confines defined by the left andright steel ring portions 186, 188. This allows for some, minor relativemovement between the steel ring assembly 184 and the ceramic raceway182. A radial gap 190 between the two is shown in FIG. 8 and allows forexpansion of both the steel ring assembly 184 and, to a lesser extent,the inner ceramic raceway 182. The left and right steel ring portions186, 188 are connected or coupled together by means of threading 192 orthreaded engagement such as 174 of FIG. 5. The assembly process matesthe parts at room temperature and then heats the assembly. A controlledtorque is then applied to pull the assembly together axially. Thisplaces the ceramic ring in compression due to the conical interface.During the heating stage, the inner ceramic raceway 182 can be brazed tothe left and right steel portions 186, 188 at their conical interface.The conical interface can be optimized to have low stiffness at the thinsections of the ceramic to prevent over stressing the ceramic ring bycontrolling the wall thickness in the axial plane. As the assembly isthen cooled to room temperature the low expansion rate ceramic is placedin axial and radial compression. The left and right steel portions 186,188 can be castellated and/or have a bellows construction at the innersteel ring assembly 184 corner to isolate the bulk of the steel ringsfrom the ID (inner diameter) press fit mount interface at the ID of theleft and right steel portions 186, 188.

[0046] The devices described above provide industrial applicability byproviding one or more of the following benefits or uses. In particular,a better bearing may be provided for operation in mechanically hostileenvironments, including a 100% ceramic contact surface bearing for suchenvironments. The ceramic ball bearing has 100% ceramic contact surfacesmay also be used in other, possibly mechanically and/or environmentallymilder environments. The ceramic ball bearing assembly prevents tension,particularly destructive tension, from being applied to ceramiccomponents of a ceramic ball bearing assembly. The ceramic ball bearingassembly can be subject to heating and cool down without sufferingdestructive tension upon the ceramic portions thereof. The ceramic ballbearing assembly holds the ceramic raceway components in compression byattached steel components and the ceramic ball bearing assemblymaintains residual compression upon the ceramic raceway components byattached metal components or the like.

[0047] While the present invention has been described with reference toa preferred embodiment or to particular embodiments, it will beunderstood that various changes and additional variations may be madeand equivalents may be substituted for elements thereof withoutdeparting from the scope of the invention or the inventive conceptthereof. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from the essential scope thereof. Therefore, it isintended that the invention not be limited to particular embodimentsdisclosed herein for carrying it out, but that the invention includesall embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A ceramic bearing assembly (20) for providingangular translation between adjoining parts, comprising a first outerceramic raceway (22) held in compression by a first outer support; asecond inner ceramic raceway (24) held in compression by a second innersupport (30); a first ceramic rolling element (26) trapped between thefirst outer ceramic raceway (22) and the second inner ceramic raceway(24); and the first ceramic rolling element (26) rotating when angulartranslation occurs between the first outer ceramic raceway (22) and thesecond inner ceramic raceway (24); whereby friction between theadjoining parts is reduced with the ceramic bearing assembly (20) by useof ceramic material and the first outer ceramic raceway (22) and thesecond inner ceramic raceway (24) are generally not subject todestructive tensile stress and the tensile stresses which reside in theceramic raceways are well within the failure limit for such ceramicmaterials.
 2. The ceramic bearing assembly as set forth in claim 1,wherein the first ceramic rolling element is selected from the groupconsisting of: balls, needles, and rollers.
 3. An inner raceway for arolling bearing, comprising: a ceramic raceway (24); first and secondretaining supports, the first retaining support (30) oppositely opposedto the second retaining support (28) on opposite sides of the ceramicraceway (24); the first and second retaining supports bonded to theceramic raceway (24); and the first and second retaining supportsradially compressing the ceramic raceway (24) and producing acceptablylow tensile stress upon the ceramic raceway despite elevatedtemperatures arising from use of the ceramic raceway or from ambientenvironmental conditions; whereby the ceramic raceway (24) is generallysubject to continuous compression and is protected from destructivetensile stresses by the first and second retaining supports and theceramic raceway is attachable to a shaft via the first and secondretaining supports, thermal expansion of the shaft occurring during useof the shaft being generally insufficient to overcome the compression ofthe ceramic raceway by the first and second retaining supports.
 4. Araceway for a rolling bearing as set forth in claim 3, furthercomprising: the first and second retaining supports extending inwardly(34) past the ceramic raceway; and the first and second retainingsupports attachable to a shaft.
 5. A raceway for a rolling bearing asset forth in claim 3, further comprising: the first and second retainingsupports brazed (96) to the ceramic raceway.
 6. A raceway for a rollingbearing as set forth in claim 5, further comprising: the first andsecond retaining supports brazed to the ceramic raceway while the firstand second retaining supports are in a warm condition that subjects thefirst and second retaining supports to thermal expansion.
 7. A racewayfor a rolling bearing as set forth in claim 3, further comprising: theceramic raceway being silicon nitride.
 8. A raceway for a rollingbearing as set forth in claim 3, further comprising: the first andsecond retaining supports being steel; the first and second retainingsupports each bonded to the ceramic raceway by braze joints (96)selected from the group consisting of: a first braze ring, a molybdenumring, and a second braze ring, the first and second braze rings onopposite sides of the molybdenum ring; and a first braze ring coupled toa first nickel ring, a second braze ring coupling the first nickel ringto a first molybdenum ring, and a third braze ring coupled to the firstmolybdenum ring.
 9. A raceway for a rolling bearing, comprising: acastellated tube (52) having a first number of merlons (58) at a firstend, including a first merlon; a ceramic raceway (64), the ceramicraceway circumscribing the castellated tube (52); the first merlon (58)outwardly wrapped to engage the ceramic raceway (64); the wrapped merlon(58) acting to restrain the ceramic raceway (64) adjacent thecastellated tube (52); whereby the ceramic raceway (64) is supported andgenerally held by the first merlon (58), the ceramic raceway (64)generally not subject to tensile stresses.
 10. A raceway for a rollingbearing as set forth in claim 9, further comprising: the castellatedtube (52) having a second number of merlons (58) at a second end,including a second merlon (58), the second merlon (58) generallyoppositely opposed to the first merlon (58) across the castellated tube(52); and the second merlon (58) outwardly wrapped to engage the ceramicraceway (64) in general opposition with the first merlon (58); wherebythe ceramic raceway (64) is captured between the first and secondmerlons (58).
 11. A raceway for a rolling bearing as set forth in claim9, further comprising: a first wedge (74), the first wedge (74) trappedbetween the first merlon (58) and the ceramic raceway (64); and thefirst wedge (74) expanding when heated thereby overlapping and urgingthe ceramic raceway (64) toward the castellated tube ends and placingthe ceramic inner ring (64) in compression after cooling to roomtemperature; whereby the castellated tube ends may be formed in a forgepress and a gap defined between the castellated tube and the ceramicraceway diminishes as the first wedge expands.
 12. A raceway for arolling bearing as set forth in claim 9, further comprising: a firstsupport ring (70), the first support ring (70) circumscribing thecastellated tube (52) adjacent the ceramic raceway (64); the firstsupport ring (70) protecting the ceramic raceway (64) from the firstmerlon (58) when the first merlon (58) is outwardly wrapped to engagethe ceramic raceway (64).
 13. A raceway for a rolling bearing,comprising: a first support tube (102); a ceramic raceway (94), theceramic raceway (94) circumscribing the first support tube (102); and aconnector (98), the connector (98) coupling the ceramic raceway (94) tothe first support (102) tube in a spaced-apart relation to define a gapbetween the ceramic raceway (94) and the first support tube (102);whereby the first support tube (102) and the ceramic raceway (94) mayengage in thermal expansion and contraction generally without subjectingthe ceramic raceway (94) to tensile stress.
 14. A raceway for a rollingbearing as set forth in claim 13, the connector (98) is selected fromthe group consisting of: a bellows-like construction (98) thataccommodates thermal expansion and contraction of the first support tubeand the ceramic raceway; a pin-in-tube arrangement (130); and arod-in-loop arrangement (130);.
 15. A ceramic bearing assembly (20),comprising: an outer ceramic raceway (22) held in compression by anouter support; an inner ceramic raceway (24); a ceramic rolling element(26) trapped between the outer ceramic raceway (22) and the innerceramic raceway (24), the ceramic rolling element (26) rotating whenangular translation occurs between the first outer ceramic raceway (22)and the second inner ceramic raceway (24), the ceramic rolling element(26) selected from the group consisting of balls, needles, and rollers;first and second retaining supports, the first retaining support (30)oppositely opposed to the second retaining support (28) on oppositesides of the inner ceramic raceway (24); the first and second retainingsupports brazed to the inner ceramic raceway (24) while the first andsecond retaining supports are in a warm condition that subjects thefirst and second retaining supports to thermal expansion; the first andsecond retaining supports brazed to the inner ceramic raceway (24) whilethe inner ceramic raceway (24) is at braze temperature, thermalexpansion of the first and second retaining supports being higher thanthat of the ceramic such that the system subjects the inner ceramicraceway (24) to thermal contraction after cooling to room temperature;the first and second retaining supports extending radially inwardly (34)past the inner ceramic raceway (24); the first and second retainingsupports attachable to a shaft; and the first and second retainingsupports radially compressing the inner ceramic raceway (24) andpreventing tensile stress upon the inner ceramic raceway (24) despiteelevated temperatures arising from use of inner the inner ceramicraceway (24) or from ambient environmental conditions; whereby the innerceramic raceway (24) is generally subject to continuous compression andis protected from destructive tensile stresses by the first and secondretaining supports and the inner ceramic raceway (24) is attachable to ashaft via the first and second retaining supports, thermal expansion ofthe shaft being generally insufficient to overcome the compression ofthe inner ceramic raceway (24) by the first and second retainingsupports.
 16. A ceramic bearing assembly (50), comprising: an outerceramic raceway held in compression by an outer support; an innerceramic raceway (64); a ceramic rolling element trapped between theouter ceramic raceway and the inner ceramic raceway (64), the ceramicrolling element rotating when angular translation occurs between thefirst outer ceramic raceway and the second inner ceramic raceway (64),the ceramic rolling element selected from the group consisting of balls,needles, and rollers; a castellated tube (52) having a first number ofmerlons (58) at a first end (54), including a first merlon (58); theinner ceramic raceway (64) circumscribing the castellated tube (52); thefirst merlon (58) outwardly wrapped to engage the inner ceramic raceway(64); the wrapped merlon (58) acting to restrain the inner ceramicraceway (64) adjacent the castellated tube (52); the castellated tube(52) having a second number of merlons (58) at a second end (56),including a second merlon (58), the second merlon (58) generallyoppositely opposed to the first merlon (58) across the castellated tube(52); the second merlon (58) outwardly wrapped to engage the innerceramic raceway (64) in general opposition with the first merlon (58);the inner ceramic raceway (64) captured between the first and secondmerlons; a first wedge (74), the first wedge (74) between the firstmerlon (58) and the inner ceramic raceway (64); the first wedge (74)expanding when heated and overlapping the ceramic raceway (64) andplacing the ceramic inner ring (64) in compression after cooling to roomtemperature such that a gap defined between the castellated tube (52)and the inner ceramic raceway (64) diminishes as the first wedge (74)expands, the castellated tube (52) formable in a forge press; a firstsupport ring (70), the first support ring (70) circumscribing thecastellated tube (52) adjacent the inner ceramic raceway (64); and thefirst support ring (70) protecting the inner ceramic raceway (64) fromthe first merlon (58) when the first merlon (58) is outwardly wrapped toengage the inner ceramic raceway (64); whereby the inner ceramic raceway(64) is supported and generally held by the first merlon (58), the innerceramic raceway (64) generally not subject to tensile stresses.
 17. Aceramic bearing assembly (90), comprising: an outer ceramic raceway heldin compression by an outer support; an inner ceramic raceway (94); aceramic rolling element trapped between the outer ceramic raceway andthe inner ceramic raceway (94), the ceramic rolling element rotatingwhen angular translation occurs between the first outer ceramic racewayand the second inner ceramic raceway (94), the ceramic rolling elementselected from the group consisting of balls, needles, and rollers; afirst support tube (102); the inner ceramic raceway (94) circumscribingthe first support tube (102); a connector (98), the connector (98)coupling the inner ceramic raceway (94) to the first support tube (102)in a spaced-apart relation to define a gap between the inner ceramicraceway (94) and the first support tube (102); and the connector (98)selected from the group consisting of: a bellows-like construction (98)that accommodates thermal expansion and contraction of the first supporttube and the inner ceramic raceway; a pin-in-tube arrangement (130); anda rod-in-loop arrangement (130); whereby the first support tube (102)and the inner ceramic raceway (94) may engage in thermal expansion andcontraction generally without subjecting the inner ceramic raceway (94)to tensile stress.
 18. A ceramic bearing assembly, comprising: an outerceramic raceway held in compression by an outer support; an innerceramic raceway (182); a ceramic rolling element trapped between theouter ceramic raceway and the inner ceramic raceway (180), the ceramicrolling element rotating when angular translation occurs between thefirst outer ceramic raceway and the second inner ceramic raceway (180),the ceramic rolling element selected from the group consisting of balls,needles, and rollers; a first support tube (186) with a wedge or conicalouter diameter flange face and a inner diameter wedge or conical surfacewith a thread (192) cut on the conical surface such as a camera releasethread; the inner ceramic raceway (182) circumscribing the first andsecond support tubes inner diameters; a second support tube (188) with awedge or conical outer diameter flange face and a inner diameter wedgeor conical surface with a thread (192) cut on the conical surface suchas a camera release thread that mates with the conical thread (192) ofthe first support tube; the first and second support tubes are torquedtogether at a high temperature and then anti rotated such that the innerdiameters of the first and second support tubes may engage in press fitexpansion and contraction generally without subjecting the inner ceramicraceway to tensile stress.